European Water 58: 203-208, 2017. © 2017 E.W. Publications Critical review of adaptation strategies for the restoration of Lake Koronia D. Malamataris1*, E. Kolokytha1, I. Mylopoulos1 and A. Loukas2 1 Laboratory of Water Resources Management, Department of Civil Engineering, Aristotle University of Thessaloniki, University Campus, 54124 Thessaloniki, Greece 2 Laboratory of Hydrology and Aquatic Systems Analysis, Department of Civil Engineering, University of Thessaly, Pedion Areos, 38334 Volos, Greece * e-mail: [email protected] Abstract: Lake Koronia water basin, located in Northern Greece, depicts a characteristic example of non-sustainable water management case in Greece. The irrational pumping for irrigation in the catchment resulted in the overexploitation of groundwater resources and a serious decrease in the runoff to lake Koronia. Furthermore, the reduction of the mean annual precipitation and the increase of the mean annual temperature, and, therefore, the evaporation that were being observed in the area, due to climate change, are expected to further deteriorate the already distributed water balance of the lake. UTHBAL model along with MIKE SHE and MIKE HYDRO BASIN models are utilized in the present study for the calculation of the historical (1970-1999) and future (2020-2049, 2070-2099) water balances of lake Koronia. The water balance of the lake for the long-term time period was found to be negative even after the implementation of the adaptation measures that have been proposed in the most recent revised Master Plan for the restoration of the lake. An assessment of the efficiency of the most important measures that have already been implemented, in terms of decreasing the future water deficit of the lake, is carried out. The paper concludes that even after the implementation of the measures the water balance of lake Koronia still remains negative for the long-term future period and so complementary adaptation measures should be implemented in order to restore the negative water balance of the lake. Key words: Lake Koronia, water balance, adaptation measures, climate change, Master plan 1. INTRODUCTION Lake Koronia case study is a complex problem that needs an integrated approach taking into consideration social, technical, environmental, political and economic aspects in order to be efficiently resolved. In terms of water quality, many studies have been carried out (e.g. Perivolioti et al., 2016; Moustaka-Gouni et al., 2012) about ecological changes that have been occurred in lake Koronia during the last decades threatening its ecosystem. In terms of water quantity, the number of studies regarding the water balance problem of the lake are limited. In their studies, Manakou et. al. (2013) developed a mathematical programming approach to restore the water balance of the hydrological basin of lake Koronia and they concluded that investment options including the water transfer from larger water sources, the creation of irrigation networks and canals and provision of subsidies to promote alternative land use for agriculture need to be taken. Kolokytha (2010) examined the contribution of Water Framework Directive and EU Common Agricultural Policy application in Lake Koronia towards the rehabilitation of its water balance in the future and she concluded that both European Policies can help to reduce the water problem of the lake but cannot solve it themselves. Mylopoulos et al. (2007) developed a groundwater model to simulate the lake Koronia-aquifer interaction and they suggested that a combination of a project recharging the lake with groundwater and water saving measures in the agricultural sector must be implemented to confront the water depletion of the lake. 2. STUDY AREA Mygdonia water basin is located in Northern Greece and it belongs to the Water District of 204 D. Malamataris et al. Central Macedonia. The water basin covers an area of 2.061,48 km2 and the mean elevation is 338 m. Lakes Koronia and Volvi are located at the lowest part of the basin at about 10 km and 35 km eastern of the city of Thessaloniki. Both lakes compose a wetland that affects and, also is being affected by the current economic activities in the whole catchment. The wetland is protected by several international and national laws. In particular, it constitutes a “Wetland of International Importance” (Ramsar site), a “Special Protection Area” (Directive 79/409/EEC), a “Site of Community Importance” (Directive 92/43/EEC) and a “National Wetland Park of Lakes Koronia – Volvi and Macedonian Tempi”. Mygdonia catchment (Figure 1) was divided into the Koronia subcatchment (768.11 km2) and the Volvi subcatchment (1.293,37 km2). Afterwards, each one of them was further divided into six and thirteen subcatchments respectively in order for the surface water bodies to be more efficiently studied. Figure 1. The nineteen subcatchments of the Mygdonia catchment 3. CALCULATION OF THE WATER BALANCE OF LAKE KORONIA An integrated hydrological study has been carried out for the simulation of water inflows and outflows to lake Koronia. In particular, three different models have been applied: the UTHBAL hydrological model for the simulation of the surface hydrological processes, the MIKE SHE model for the simulation of the hydraulic interaction between lake Koronia and groundwater, and finally, the MIKE HYDRO BASIN model for the simulation of the water balance of the lake. 3.1 Simulation of surface hydrological processes The conceptual hydrological model UTHBAL (University of Thessaly water BALance model) (Loukas et al., 2007) has been used for the calculation of the hydrological parameters for the historical period 1970-1999. UTHBAL model has six parameters to be optimised in order to estimate the hydrological cycle parameters. The model uses monthly time-series of areal precipitation, mean areal temperature, mean areal potential evapotranspiration and observed monthly discharge values as inputs. Mean areal surface precipitation and temperature for the whole Mygdonia catchment were calculated European Water 58 (2017) 205 equal to 518.69 mm/year and 13.27 ºC using the Thiessen method along with the precipitation gradient method, and the temperature gradient method respectively. Mean areal potential evapotranspiration was calculated using the Thornthwaite method, and, finally observed monthly discharges of Mpogdanas, Analipsi, Lagkadikia, Sxolari, Gerakarou and Vasiloudi streams as measured at the outfall points for the period 1995-1999 (Veranis and Katirtzoglou, 2001) were also imported to the model. The model was calibrated and validated with the observed monthly discharges of the six streams and the monthly hydrological cycle components for each one of the six subcatchments were calculated. The six hydrological parameters of the UTHBAL model were then transferred to the other thirteen subcatchments based on land use, slope and geological criteria in order to estimate the hydrological parameters of these subcatchments too. The main outputs of the model are monthly time series of actual evapotranspiration, surface runoff and groundwater recharge. Mean annual runoff to lake Koronia was calculated equal to 7.49 hm3/year. It must be noted that only limited water amounts (about 6 hm3/year) flow into lake Koronia after the year 1985 due to the extensive pumping in the surrounding area that has resulted in the increase of recharge to groundwater and decrease of the surface runoff (Veranis and Katirtzoglou, 2001). 3.2 Simulation of groundwater resources Mygdonia catchment is an endorheic basin in hydrogeological terms (Mpallas, 2007). The groundwater flow follows the longitudinal axis of the catchment; in normal conditions groundwater flows from Koronia subcatchment to Volvi subcatchment, and then a part of this discharge outflows to a neighbouring subcatchment at the eastern part of the Mygdonia catchment. Mygdonia groundwater simulation was performed using the MIKE SHE model. At first, the catchment was divided into six groundwater subcatchments (Koronia, Volvi, Mavrouda, Kroussion- Kerdyllion, Nteve Koran and Xolomonta-Oraiokastrou) for the analytical study of groundwater resources. Geometrical and hydraulic parameters, namely upper level, lower level, horizontal hydraulic conductivity, vertical hydraulic conductivity, specific yield and storage coefficient were imported to the groundwater model for each layer of each one of the above six groundwater subcatchments. Also, daily time-series of recharge to groundwater and pumping for agricultural, livestock, tourist and household water needs were also imported to the model. The whole catchment of Mygdonia was divided into 8,244 grid cells (500x500 m the area of each grid cell) and the simulation was carried out from 01 October 1970 until 30 September 2000 with a daily time step. It was found that there is no hydraulic interaction between groundwater and lake Koronia. 3.3 Simulation of lake Koronia Lake Koronia covers a maximum area of 46.03 km2, its bed elevation is 66.50 m above the sea level and it has a maximum depth of 6.50 m. Lake Volvi is located at 11 km eastern of lake Koronia and its bed elevation is 52.50 m lower than the one of lake Koronia. The overflow of lake Koronia flows by gravity through an artificial drainage ditch called River Derveni and it outflows to lake Volvi (Figure 1). Nowadays, the physical interaction between the two lakes has been interrupted because of the tremendous decline of the water depth of lake Koronia. Mean annual precipitation and evaporation for the lake Koronia were calculated equal to 20.61 hm3/year and 29.51 hm3/year respectively from 1970 until 1999. As for the pumped water from the lake, according to the article 4, paragraph 2 of the Joint Minesterial Decision 6919/2004, pumping from lake Koronia is prohibited. Simulation of inflows and outflows to lake Koronia was performed using the MIKE HYDRO BASIN model at a daily time step for the historical period 1970-1999. It was found that lake 206 D. Malamataris et al. Koronia had an average negative water balance of -1.41 hm3/year. The water level variation of lake Koronia for the period 1970-1999 is presented in Figure 2.